Air filter



FIG. 1 is a front, top and right side perspective view of an air filter showing our new design;

FIG. 2 is an inverted, rear, bottom and left side perspective view thereof;

FIG. 3 is an enlarged, partial view similar to that of FIG. 1;

FIG. 4 is an enlarged partial view similar to that of FIG. 2;

FIG. 5 is a top, front and right side perspective view of a second embodiment of the air filter;

FIG. 6 is an inverted, rear, bottom and left side perspective view of FIG. 5;

FIG. 7 is an enlarged partial top plan view of FIG. 5; and,

FIG. 8 is an enlarged partial bottom plan view of FIG. 5. 

The ornamental design for an air filter, as shown and described. 